U.S. Pat. No. 3,620,584, issued Nov. 16, 1971 for "Magnetic Fluid Seals", describes a modular magnetic-fluid seal wherein a magnetic fluid is captured in a gap between a rotating shaft and a stationary housing in which the shaft is journalled. The magnetic fluid thus captured, is designed to provide a leak-proof hermetic seal between the rotating shaft and the housing.
There are a number of advantages provided by a magnetic seal structure, namely, there is no leakage of the sealed substance across the magnetic-fluid seal, there is no rubbing or wear at the mating surfaces where the seal is formed, and structurally a magnetic seal is a very simple device. However, there are still a number of unanswered problems involved in the design and use of magnetic seals, the most significant of which is the capacity of a given magnetic seal construction to withstand differential pressure .DELTA.p across the seal. To resolve this problem, the present invention was devised.